Whooping cough is an infection of the lining of the airways. It mainly affects the windpipe and the two airways that branch off from it to the lungs.
Daybreak's Health Editor Dr Hilary Jones explains;
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Andreea Cristea, 29, remains in a critical condition after being rescued from the Thames after a terror attack along Westminster Bridge.
The Prime Minister has praised the former soldier's "huge professionalism" in trying to save the life of Pc Keith Palmer.
The man who carried out the Westminster attack is thought to be British born and was once investigated by MI5, the Prime Minister has said.